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November 1, 2012
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Outlook for winter weather: El Nada?

A weakening El Nino weather pattern could mean another subpar snow year for Colorado for the 2012 to 2013 winter season, which could compound the drought Colorado has been in since last year's dry winter.

"We are rolling the dice this year," said Joe Ramey, a meteorologist with the National Weather Service in Grand Junction.

"Temperatures in October were above normal," according to Kyle Frebyn, a meteorologist with the National Weather Service in Boulder. Colorado remains in a drought and the drought is expected to continue through the upcoming winter, he said.

Meteorologists speculate that weakening El Nino conditions are starting to indicate Colorado may experience a neutral or "No Nino" winter.

A dry fall, such as the one we experienced this year, usually leads to No Nino years, according to Ramey.

No Nino years are also considered to be wild card years, meaning there is a chance the weather could go either way and we may have a wet winter season. However, past climate data suggests that No Nino years are more likely to be dry years.

"Extreme event analysis says No Nino years are wild card years and can be very wet but most often they're dry, and when they're dry, they are really dry," Ramey said.

El Nino, La Nina, and El Nada

El Nino Southern Oscillation (ENSO), or simply El Nino, is a weather phenomenon that spawns from the fluctuation of water temperatures in the Equatorial Pacific ocean. Warmer than normal ocean temperatures cause El Nino, which usually will bring more precipitation to the southern parts of Colorado.

La Nina is El Nino's counterpart and spawns from colder than normal ocean temperatures in the Equatorial Pacific. La Nina, which Colorado has experienced for the past two years, will usually drop more snow in the Northern Rockies.

Neutral or "No Nino" years occur when there are no abnormal fluctuations in the water temperatures of the Equatorial Pacific.

The jet stream that pushes the precipitation created by El Nino and La Nina have a preferred position, while the jet stream during neutral years does not, according to Ramey.

Jet streams during neutral years can be oriented anywhere and therefore the destination of precipitation from the Pacific is less predictable.

"If we happen to be in the storm track we will get snow," Ramey said.

There have been more neutral years in the past than El Nino or La Nina years, according to Ramey.

Neutral years in the past have been characterized by extremely dry weather and are usually preceded by dry falls, such as the one we are experiencing this year.

There have been four No Nino years in the past 15 years, according to Ramey. One of those years was 2001-2002 when the infamous Hayman fire, Colorado's largest fire, took place.

Numerous fires that took place around Colorado this year were partially due to the dry conditions that existed from the drought.

"The dry year last year followed by a dry year this year would be unprecedented in our history," Ramey said.

Earlier predictions for this year were for an El Nino year, but the dry fall signals a weakening El Nino pattern, which is expected to turn into a neutral pattern next month.

In neutral years in the past, there has been a bump in precipitation during December and April, according to Ramey.

As meteorologists compare the climate of previous years to current conditions, weather predictions for coming months posse the potential to be wrong and are therefore referred to as "low confidence," Ramey said.

Theories exist that changing and worsening weather patterns are due to global climate change.

"As we continue to see the climate change, we will see more and more extreme weather," Ramey said.


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The Sky-Hi News Updated Nov 1, 2012 06:40PM Published Nov 1, 2012 06:39PM Copyright 2012 The Sky-Hi News. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.